Radio receiver



Nov. 24, 1936. I M, A. MCLENNAN 2,061,736,

RADIO RECEIVER Filed June 25, 1932 INVENTOR Miles .l lcLennan HISATTORNEI Patented Nov. 24, 1936 UNITED STATES PATENT OFFIE 7 Claims.

My invention relates to radio receivers and, more particularly, toreceivers of the so-called remote control type.

It is an object of my invention to provide a light, portable tuning orstation selecting unit capable of being moved from place to place in aliving room, or a similar location, in order that accurate tuning of aradio receiver may be accomplished from any desired point therein.

Another object of my invention is to provide a remote control radioreceiver so constructed that the portions thereof not involved in thetuning operation may be disposed at a distance from the tuning unitproper Without militating against the efficiency of the systemconsidered as a Whole.

A still further and more specific object of my invention is to provide,in a radio receiver of the type preferred to, a single manually operableelement that shall function both as a volume control and as an on-oifswitch.

In brief, a receiving system embodying my invention preferably comprisesthree separate units, namely, (1), a tuning-control unit including asignal receptor, such as a loop antenna, an oscillator, a firstdetector, (2) a main amplifier and 7 power supply device, and (3) aloudspeaker. The tuning unit preferably is enclosed in a small box about10"x5"x6", and the tuning condensers therein are interconnected foruni-control. The pickup loop is mounted inside the tuning controlcabinet and, for ordinary signal reception, need not be over 5" square.

It is, of course, feasible to dispose the tuningcontrol unit adjacent toa lead-in from an outside antenna, if desirable, but I have found thatvery satisfactory reception may be had using only the loop in thecontrol unit.

The main amplifier I, preferably, dispose in the basement of the housewherein the installation is made and I connect it to the tuning unitthrough a five-wire cable, which cable not only supplies power for theoperation of the three tubes in the tuning unit but also conveys theintermediate frequency signal from the tuning unit to the amplifier.

The constants of the cable are so chosen, i. e., the inductance anddistributed capacity thereof, that, together with an input coil disposedin the main amplifier, the said cable provides maximum transmissionefiiciency for the intermediate frequency.

The intermediate frequency portion of the main amplifier is a completelyshielded unit, preferably utilizing thermionic tubes of the scree gridtype, such as those commercially known as UX222, and operates at afrequency of about 160 kilocycles. The audio frequency amplifier portionand the power unit are orthodox in substantially all respects, as isalso the dynamic itself, however, both as to its organization and itsmethod of operation, together with additional objects and advantagesthereof, will best be understood from the accompanying drawing, thesingle figure of which is a diagrammatic view of a complete radioreceiving system constructed and arranged according to my invention.

Referring to the drawing, a radio receiving system constructed accordingto a preferred embodiment of my invention comprises a portable tuningcontrol unit indicated by a dotted line I, a'portable loudspeaker 3disposed within soundrange of the said unit, and a remotely situatedamplifier and power supply device indicated by a dotted rectangle 5. Inthe drawing, the remote location of the amplifier and power supply unitas, for example, in the basement of a dwelling house or the like whereinthe system is installed, is indicated by a partition or fioor l, and bythe fact that portions of the conductors interconnecting the severalelements are shown in dotted lines.

The portable tuning control unit includes a frequency converting tube,or first detector, 9, an oscillator tube ll, an intermediate amplifiertube l3, and a signal receptor such as a small loop IS. The tuningcondensers l1 and I9, respectively, associated with the first detectorand the oscillator, are preferably of the straight line frequency typeand are interconnected for simultaneous actuation.

The several thermionic tubes 9, H, and I3 may be inter-connected forsignal transfer purposes in any manner well known to those skilled inthe art, although I have found by experience that the connections shownin the drawing offer certain advantages. For example, it will be notedthat the locally generated oscillations are impressed on the platecircuit of the frequency converting tube through a conductor 2| leadingto the low potential end of a beat-frequency output circuit constitutedby a choke coil 23 and a condenser 25, this particular mode ofconnection being somewhat advantageous in that it, to some extent,minimizes the deleterious effect upon the tuning of the radio frequencystage occasioned by the tuning of the oscillator, and also tends tominimize radiation of the locally generated oscillations.

A choke coil 26 is preferably interposed in the plate potential supplyconnection to the first detector tube 9, the constants of this coilbeing so chosen that it offers a high impedance to the 10- callygenerated oscillations from the oscillator tube H.

The tubes in the tuning control unit are supplied with cathode heatingpotentials over a plurality of common conductors 27 and 29, of which theconductor 29 extends to the positive pole of a battery 3| disposed inthe amplifier unit 5, the connection including the winding of a relay33, While the other conductor, 21, extends from the cathodes to a fixedcontact 35 of a switching de vice 3'1, mounted in the remote controlunit. The switching device includes a resilient contact arm 39 fromwhich a conductor 49 extends to the negative pole of the battery.

The switching device, it will be noted, in addition to the contactsincluded in the cathode heating circuit, also comprises a potentiometerconstituted by a resistor 4! and a movable contact 43. The upper end ofthe resistor is connected to the plate of the first detector [3 througha condenser 45. When the movable contact 43 is in the position shown inthe drawing, the oathode heating circuit of the several tubes in thesystem is broken and, at the same time, since the movable contact isconnected conductively to the cathode of the first detector, thepotentials impressed upon the input circuit of the beat frequencyamplifying portion of the main amplifier are minimum.

The main amplifier includes a plurality of beat frequency amplifiertubes 47, 49, and 5i, a second detector tube 53, and a plurality ofaudio frequency amplifier tubes 55 and 57, the tube 51 being of thepower type, and the tubes 4'! and 49, as well as 49 and 5!, beingconnected through similar tuned impedance networks 59. The first orinput tube of the beat frequency amplifier is coupled to the outputcircuit of the tube l3 over the common conductor 21 and a conductor 6|,the latter extending between the plate of amplifier tube l3 and the highpotential end of an impedance device 63. The constants of the cableincluding the several conductors thus far enumerated and the impedancedevice are so chosen that attenuation of the beat frequency is minimum.

The detector tube 53 may be coupled in any desired manner to the thirdbeat frequency amplifier tube 55, and the audio frequency amplifiertubes 55 and 51 may be connected by a transformer 65, the first of thesetubes being coupled to the output circuit of the detector in any desiredmanner, as by a network El. The specific coupling network 67 shown inthe drawing, and which I have found quite satisfactory, includes aseries resonant circuit 59 tuned to the beat frequency, a couplingresistor H, a blocking condenser 13, and an audio frequency choke coill5. This increases the efficiency of rectification and, at the sametime, does not attenuate the high audio frequencies such as does asimple by-pass capacitor as heretofore known.

Grid bias potential for the second detector 53 and the first audiofrequency amplifier 55 may be provided by a small biasing battery 11,the positive terminal of which is adjustably connected to a resistor 19disposed across the cathode heating current supply leads 2'! and 29. Themanner in which bias potential is applied to the grid of the poweramplifier tube will be hereinafter referred to in more detail.

In order that the battery 3| supplying cathode heating potentials to allof the tubes in the system with the exception of the power amplifier maybe kept charged I, preferably, provide a full wave rectifier 9i andfloat the battery across the output terminals thereof. The rectifier issupplied with high potential alternating current from a powertransformer 83, one terminal of the primary winding of which is directlyconnected to a power line, and the other terminal of which, over anadjustable resistor 81, may be connected to the remaining power supplyline over a circuit including a plurality of contacts 89 and 9i, carriedby the armature of the relay 33 interposed in the cathode heatingcircuit.

Plate potentials for all of the tubes in the system are supplied from arectifier 93 energized from a power transformer 95, the primary windingof which is connected in parallel with the primary winding of thetransformer which feeds the battery charging rectifier. The rectifier 93has an output circuit serially including a choke coil 81, the fieldwinding 99 of the loudspeaker 3, and an output resistor IOI, one end ofwhich is connected to the negative terminal of the rectifier 93 and,preferably, is provided with a ground connection.

The power transformer includes an additional secondary winding I03 forthe purpose of supplying cathode potential to the power amplifier 57, aresistor I05 being connected across this winding, and having a mid tapfrom which a connection l0! extends to the negative terminal of therectifier output resistor I01 over a biassupply resistor I09.

Upon reference to the drawing, it will be noted that the space currentflowing in the power amplifier tube 51 returns to the negative end ofthe rectifier output resistor over a path including the resistor Q05connected across the cathode heating winding )3 and the resistor I09connected between the said winding and. the negative end of therectifier output resistor IDI. It will also be noted that the grid ofthe power amplifier tube is connected to the grounded negative end ofthe rectifier output resistor l9! over a circuit including theconductors 21, and 40, and, therefore, is maintained at a potentialnegative with respect to the cathode by reason of the drop across theresistor I99.

In order that the operation of my improved receiving system may beclearly understood, let it be assumed that the on-off switch 3"! in thetuning control unit is in the position shown in the drawing. Such beingthe case, the cathode heating circuits of all of the tubes except thepower amplifier are interrupted and the relay 33 is not energized. If,now, the movable contact device 43 is adjusted away from the positionshown in the drawing in the direction indicated by the arrow, thecontacts 35 and 39 of the switch are permitted to close. The closing ofthese contacts supplies potential to the oathodes of the tubes over theconductors 2'! and 40 and, simultaneously therewith, the relay 33 isenergized, causing the contacts 89 and 9| to close. The closing of therelay contacts completes a circuit through which the primary windings ofthe several power transformers 83 and 95 75 are connected to the powersupply lines and the rectifiers 93 and BI deliver, respectively, platecurrent to the tubes in the system and charging current for the cathodeheating battery 3|.

Obviously, the secondary winding IE3 of the transformer 95, at the sametime, supplies cathode potential to the power amplifier tube 5'! and theentire system is in condition for the reception of signals.

During signal reception, the tuning control unit i may be moved fromplace to place without militating against signal reception, the range ofmovement of the device being circumscribed only by the length of thecable interposed between it and the point at which the said cable entersthe room wherein the unit is disposed.

The loudspeaker 3 also may be moved to any convenient locationdetermined by the length of the cable connecting it to the outputcircuit of the main amplifier.

For volume control purposes, the movable element 43 of the on-off switch31 is moved further and further toward the free end of the resistor 4|associated therewith, such movement serving to increase the volume andmovement in the reverse direction serving to reduce the volume.

It will, accordingly, be appreciated from a consideration of theforegoing description of a preferred embodiment of my invention that asystem constructed in accordance therewith offers many advantages. Forexample, my improved system lends itself admirably to installation indwelling houses where the living room is too small to accommodate aradio receiver of the usual console type. Furthermore, by reason of themobility of the tuning control unit, it may be placed in any convenientlocation in the said living room such, for example, as adjacent to thefavorite armchair of the householder and, from that position, thecontrol of signal reception may be had with minimum effort. Many otheradvantages will be apparent to those skilled in the art to which myinvention pertains.

Although I have chosen a preferred embodiment of my invention forpurposes of illustration, it is to be clearly understood that I am notrestricted thereto, my invention being limited only by the extent of theprior art and by the spirit of the appended claims.

I claim as my invention:

1. A radio receiver of the superheterodyne type comprising a portabletuning unit including means for converting an incoming signal into anamplified intermediate frequency signal, a remotely disposed seconddetector for converting the intermediate frequency signal to an audiofrequency signal, means including a cable for transferring saidintermediate frequency signal from said portable unit to said remotelydisposed second detector, and means for utilizing said audio frequencysignal.

2. The invention set forth in claim 1 characterized in that the portableunit includes an oscillator, a first detector and at least one stage ofa beat frequency amplifier.

3. The invention set forth in claim 1 characterized in that the portableunit includes at least one stage of a beat frequency amplifier inaddition to said signal converting means, and that said cable hassuitable constants for minimizing the attenuation of intermediatefrequency signals transferred thereover.

4. A radio receiver of the superheterodyne type, comprising a portabletuning unit including means for converting an incoming signal into anintermediate frequency signal and amplifying said last named signal, aremotely disposed intermediate frequency amplifier, second detector,

audio frequency amplifier and power supply device, a multi-conductorcable having suitable constants for minimizing the attenuation ofintermediate frequency signalling currents conductively connecting saidunit and said second detector, and a loudspeaker connected to saidamplifier and power supply device to receive energizing potentialstherefrom.

5. In a radio receiving system of the superheterodyne type, a radiofrequency amplifier, oscillator and first detector comprised within aportable housing, an intermediate frequency amplifier, second detector,audio frequency amplifier and power supply device comprised within aremote housing, a sound reproducing unit connected to said audiofrequency amplifier and power supply device, and means includingconductive connections between said portable housing and said remotehousing for minimizing the attenuation of intermediate frequencycurrents which are transferred from said first detector to saidintermediate frequency amplifier.

6. In a superheterodyne receiving system, a portable unit containing atuning unit, frequency converter and intermediate frequency amplifier, aremotely situated unit containing a further intermediate frequencyamplifier, second detector, audio frequency amplifier, and power supplydevice; a multi-conductor transmission cable conductively connectingsaid portable unit with said remotely situated unit; and a soundreproducer connected to said audio frequency amplifier; the electricalconstants of the conductors in said transmission cable being such as tominimize the attenuation of intermediate frequency currents traversing acertain pairof said conductors there in, and the tuning unit andfrequency converter being adapted to effect suitable interaction betweena desired incoming signal and local oscillations for producingsignalling currents of a given intermediate frequency band, whereby saidcurrents may be transmitted to said remotely situated unit for derivingaudio frequency currents to be impressed upon said sound reproducer.

7. A remote control superheterodyne receiver comprising, in combination,a unitary control device including frequency converting and amplifyingelements, an amplifier for the conversion frequency, further means foramplifying said conversion frequency remotely located with respect tosaid control device, means for transmitting amplified conversionfrequency signals from said device to said last named means, a signaldetector connected with said further amplifying means to derive themodulation signal therefrom, a modulation signal amplifier and soundoutput device for reproducing the output from said signal detector,power supply means for said receiver connected with said control device,said amplifiers and said sound producing device to energize the same,and means in said control device for operating said power supply meansto energize said receiver.

MILES A. MoLENNAN.

